Thanks sailingdog. I sure wish I knew the make and model. None of my Gulf 32 materials specify the wheel and though it is an Edson pedestal, the wheel is not, from what I can tell. I have gone through the Edson archives and found nothing like this wheel; all of theirs seem to use the nut attachment system. I welcome all suggestions of what make and model of wheel this is!
Set pin? I wondered about that but checked and found that the pin does not go all the way through the wheel hub and shaft, which I think it would need to do to be a set pin, no? Whatever it is, it terminates at the shaft, and so I conclude it must be removable somehow from above, and thus a set screw of some sort.
I'm encouraged by the recommendation to check metric allens and plan to try that ASAP. I'll report back when I find out. I'm a big fan of Occam's razor